Conventional diesels, derived from crude petroleum, are used in a variety of applications, such as in transportation, power generation etc. However, the diesel run vehicles and other stationary equipments are associated with pollution, specially smog forming nitrogen oxides (NOx) emissions and particulate matter (PM) or soot. This environmental concern has been the main guiding factor for research in finding the economical solutions that could reduce pollution emitted from diesel-powered engines. Several chemical additive approaches have been tried in past with the main object of reducing emissions from existing engines, new and old, without expensive engine modifications or replacements. It is known in the literature that internal combustion engines can be run on mixture of water and fuel to produce lower NOx, hydrocarbon and particulate emissions per unit of power output. Water is inert towards combustion, but acts to lower peak emission temperatures, which result in significant reduction of NOx formation. Though water can also be separately injected into the combustion chamber, but the hardware costs are high. Water can however be added to fuel as an emulsion, but the stability of emulsion has historically been a problem. The problems of making water-fuel emulsions include instability of emulsions, high cost of emulsifiers, larger amounts of emulsifiers required to produce the emulsions and non-availability of non-toxic biodegradable emulsifiers.
Due to the concerns about the emissions from diesel run engines, several options have been explored and these include engine modifications and modifications in the fuels. Alcohol and water have been studied in details as their addition in fuel could reduce emissions from the engines to an appreciable extent.
Publication No., WO 97/34969 describes stable a diesel-water emulsion by using a surfactant system consisting of sorbitan sesquioleate, a polyethylene glycol mono-oleate and a nonylphenol ethoxylate. The surfactant system had a HLB of 6-8.
WO 48123,2001 of Elf ANTAR, France describes an emulsifying system to make stable hydrocarbon-water emulsion. The system contained a sorbitol ester, polyethoxylated fatty acid ester and poly alkoxylated alcohols.
A Hungarian, PCT application No. WO 12285,1998 described water containing fuel compositions useful for internal combustion engines. An emulsifying system was disclosed and it essentially consisted of coconut fatty acid ester, polyethylene glycol derivatives of coconut oil fatty acid esters, sodium lauryl sulphate and glycerin. The amount of emulsifying mixture was in the range of 5-15% for dispersing 10-40% distilled water in the hydrocarbon fuel.
Several other emulsifying systems useful for incorporation of water in hydrocarbon have been described e.g. U.S. Pat. No. 4,729,769; U.S. Pat. No. 4,594,111; U.S. Pat. No. 4,100,097; U.S. Pat. No. 5,021,183; U.S. Pat. No. 5,443,757 & U.S. Pat. No. 4,917,883. A European patent application EP 1152049,2001 discloses a method for preparing water in hydrocarbon micro emulsion by use of a surfactant. Both micro & macro emulsions could be prepared depending upon the amount of water to be dispersed and the type of emulsifying additives. Thus, micro emulsion were reported utilizing 5% volume of water in diesel and the surfactant package consisted of lipophilic neat oleic acid, lipophilic ethoxylated oleic acid, lipophilic sorbitan ester monoleate, lipophilic ethoxylated oleic acid and a hydrophilic oleic acid completely neutralized with monoethanol amine. The application of the above surfactant system resulted in micro emulsions but it required 8% volume of the surfactant mixture and intense mechanical agitation. For incorporation of 10% volume water into the diesel phase, 14% volume of the surfactant mixture and intense manual agitation was necessary. Even 15% water could be micro emulsified in diesel, however very large dose of surfactant mixture (20% volume) was required. Similarily, several other patents describe the formation of stable micro emulsion of water and hydrocarbon fuel, which at times have larger amounts of surfactants as compared to the water content. Efforts in the area of the micro emulsion of water in hydrocarbon fuels are described in U.S. Pat. No. 5,743,922, WO 34969(97); U.S. Pat. No. 5,873,916, WO 13031(99).
Inspite of the disclosures of above patents, the micro emulsified water containing hydrocarbon fuels could not gain commercial popularity, as the emulsions, which are suitable as combustible fuel, need very large amounts of surfactants and/or other stabilizing agents. In view of these limitations of the micro emulsions a lot of research work has been carried out and reported for formation of stable cost effective micro emulsions of water in hydrocarbon fuels.
In order to reduce the amount of the surfactants and/or stabilizers and yet to get the micro emulsified fuels, a tri component system has also been explored. Wanzel et.al (U.S. Pat. No. 4,083,698) prepared a stable water in oil micro emulsions comprising (a) a hydrocarbon fuel (b) water, (c) an alcohol, and (d) a combination of surface-active agents. Examples given include diesel fuel micro emulsions where in the alcohol is methanol, ethanol or isopropanol.
The combination of surfactant must include three components (1) a long chain fatty acid salt (2) a free fatty acid, preferably long-chains unsaturated fatty acid and (3) a non-ionic surfactants like ethylene oxide condensation products and esterified products of fatty acids with ethylene oxide. A. W. Schwab in a U.S. Pat. No. 4,451,265 disclosed the formation of a hybrid fuel—a micro emulsion prepared from diesel fuel, water, alcohol and a surfactant comprising N,N-dimethylethanolamine and a long chain fatty acid derivative.
Emulsified water-hydrocarbon fuel compositions have been described in several patents. Thus, Daly et al (U.S. Pat. No. 6,280,485, 2001) describes water blended fuel compositions comprising: (A) a hydrocarbon boiling in gasoline or diesel range; (B) water; (C) a minor emulsifying amount of at least one fuel soluble salt made by reacting at least one acetylating agent having about 16-500 carbon atoms with ammonia or at least one amine and (D) a water soluble, ashless, halogen, boron, phosphorous free amine salt distinct from component C. In some formulations a co-surfactant, organic cetane improver and anti-freeze may also be used.
European patent EP 0561600A2(1993) discloses water fuel emulsions in which the emulsifier is made by reaction of (A) substituted acetylating agent and (b) ammonia and/or at least one amine. A U.S. Pat. No. 4,078,753(1987) discloses water in oil emulsion comprising (A) continuous oil phase; (B) water; (l) at least one hydro carbonyl substituted carboxylic acid & anhydride, ester or amide derivative of said acid or anhydric and (C) (II) at least one amine; and (D) an effective amount of at least one water soluble, oil-insoluble functional additive.
Several other patents, which describe the formation of water hydrocarbon emulsions, include U.S. Pat. No. 5,047,175; EP 0475620B1 U.S. Pat. No. 5,669,938: U.S. Pat. No. 6,017,368.
CNSL and its derivatives have been known for producing high temperature phenolic resins and friction elements, as exemplified in U.S. Pat. Nos. 4,395,498 and 5,218,038. Cashew nut shell liquid occurs as a reddish brown viscous liquid in the soft honeycomb structure of shell of cashew tree, Anacardium Occidentale L. Native to Brazil, the tree grows in the coastal areas of Asia and Africa. Cashew nut attached to the shell apple is gray colored kidney shaped and 2.5-4 cm long. The shell is about 0.3 cm thick, having a soft leathery outer skin and a thin hard inner skin. Between these skins is the honeycomb structure containing the phenolic material popularity called CNSL. Inside the shell is kernel wrapped in a thin brown skin, known as the testa. The nut thus consists of kernel (20-25%), the shell liquid (20-25%) and testa (2%), the rest being the shell. CNSL, extracted with low boiling petroleum ether, contains about 90% anacardic acid and about 10% cardol. CNSL, on distillation, gives the yellow phenolic derivatives, which are a mixture of biodegradable unstructured unsaturated m-alkylphenols, including cardanol. Catalytic hydrogenation of these phenols gives a white waxy material, predominantly rich in tetrahydrocardol.
Friction lining production from CNSL is also reported in U.S. Pat. No. 5,433,774. Likewise, it is also known to form different types of friction materials, mainly for use in brake lining system of automobiles and coating resins. U.S. Pat. No. 6,229,054 describes a process for hydroxyalkylation of cardanol with cyclic organic carbonates. CNSL derivatives have also been used for metal extraction, as exemplified in U.S. Pat. No. 4,697,038. In another U.S. Pat. No. 4,352,944, Mannich bases of CNSL have been described.
However, the first application of CNSL in making lubricating oil additives was disclosed by us in U.S. Pat. Nos. 5,910,468 and 5,916,850. U.S. Pat. No. 6,339,052 also describes lubricant compositions for internal combustion engines based on additives derived from cashew nut shell liquid.